Have you heard of the Tom Glazer Singing Science records? Tom Glazer (1914-2003) was a folk singer best known for the song "On Top of Spaghetti" (!!!). He started this series of albums of educational science songs. And when I was young and showed some interest in science my folks got me a few of these, and one of my buddies had a couple more of them. I thought they were fascinating, and so my future as a nerd was pretty much guaranteed from there on. Even the cover art is wonderous.
They've been out of print for several decades, but thanks to the interweb we have them back. A local fellow named Jef Poskanzer found a complete set in his parent's basement and went about making mp3 copies. Check'm out here:
I've burned the complete collection up for the twins, and the science songs have been in heavy rotation at bedtime ever since. They are really, really dated, in a fun boy scout, atomic age and musical cliche kind'a way.
And of course They Might Be Giants did a rendition of "Why Does the Sun Shine?" that has become somewhat popular.
(Note that the guitarist on the early records is Tommy Motola, later the head of Sony Music, married to Mariah Carey, and accused by Michael Jackson of being "uh... devilish".)